Cranial mononeuropathy III
Cranial mononeuropathy III is a nerve disorder. It affects the function of the third cranial nerve. As a result, the person may have double vision and eyelid drooping.
Third cranial nerve palsy; Oculomotor palsy; Pupil-involving third cranial nerve palsy; Mononeuropathy - compression type
Cranial mononeuropathy III is a mononeuropathy, which means that only one nerve is affected. It affects the third cranial (oculomotor) nerve. This is one of the cranial nerves that control eye movement. Local tumors or swelling can press on and damage the nerve.
Causes may include:
- Brain aneurysms
- Abnormal blood vessels (vascular malformations)
- Sinus thrombosis
- Tissue damage from loss of blood flow (infarction)
- Trauma (from head injury or caused accidentally during surgery)
- Tumors or other growths (especially tumors at the base of the brain and pituitary gland)
In rare cases, people with migraine headaches may have a temporary problem with the oculomotor nerve. This is probably due to a spasm of the blood vessels. In some cases, no cause can be found.
Symptoms may include:
- Double vision, which is the most common symptom
- Drooping of one eyelid (ptosis)
- Enlarged pupil that does not get smaller when a light shines on it
- Headache or eye pain
Other symptoms may occur if the cause is a tumor or swelling of the brain. Decreasing alertness is serious, because it could be a sign of brain damage or impending death.
Exams and Tests
An eye examination may show:
- Enlarged (dilated) pupil of the affected eye
- Eye movement abnormalities
- Eyes that are not aligned
Your health care provider will do a complete examination to determine the possible effect on other parts of the nervous system. Depending on the suspected cause, you may need:
- Blood tests
- Tests to look at blood vessels to the brain (cerebral angiogram, CT angiogram, or MR angiogram)
- MRI or CT scan of the brain
- Spinal tap (lumbar puncture)
You may need to be referred to a doctor who specializes in vision problems related to the nervous system (neuro-ophthalmologist).
Some people get better without treatment. Treating the cause (if it can be found) may relieve the symptoms.
Treatment may include:
- Corticosteroid medications to reduce swelling and relieve pressure on the nerve (when caused by a tumor or injury)
- Eye patch or glasses with prisms to reduce double vision
- Pain medications
- Surgery to treat eyelid drooping or eyes that are not aligned
Some patients will respond to treatment. A few cases result in permanent eye drooping or loss of eye movement.
Causes such as brain swelling due to a tumor or stroke, or a brain aneurysm may be life threatening.
When to Contact a Medical Professional
Call your health care provider if you have double vision and it does not go away in a few minutes, especially if you also have eyelid drooping.
Quickly treating disorders that could press on the nerve may reduce the risk of developing cranial mononeuropathy III.
Rucker JC. Cranial neuropathies. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley's Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 70.